Manufacture of oxids of nitrogen



UNITED STATES PATENT OFFICE.

CARL BOSCH, ALWIN MITTASCH, AND cnms'rorn BECK, or LUDWIGSHAFEN-ON-THEJ RHINE, GERMANY, ASSIGNORS, BY mnsnr. ssrenmmrrs, TO THE CHEMIQAL FOUNDATION, me, A CORPORATION or DELAWARE.

MANUFACTURE OF OXIIDS OF NITROGEN.

Patented May 24, 1921.

I --d 1,379 391 Specification of Letters Patent.

No Drawing.

To all whom it may concern.

Be it known that we, CARL Boson, ALWIN MITTAsoH, and CHIus'rorH BECK, citizens of the German Empire, residing at Ludwigshafen-on-the-Rhine, Germany, have invented new and useful Improvements in the Manufacture of Oxids of Nitrogen, of which the following is a specification.

It has been proposed to convert ammonia into oxids of nitrogen, or nitric acid, by passing ammonia together with an oxygencontaining gas, such as air or oxygen, at .a raised temperature, over oxide of the metals of the iron group, but the results hitherto obtained have varied considerably and have been generall unsatisfactory.

We have ound that we may carry out the manufacture of oxids of nitrogen by the catalytic oxidation of ammonia in a regular manner and with good yields by employing the oxid, or oxide, or mixtures of the oxids of the metals of the iron group, in separate pieces, or lumps, of which a sufficiently deep layer should be used. The size. and shape of the pieces, or lumps, may vary, for instance, according to the width of the contact tube, or furnace, and it is often advantageous to heat the pieces, or lumps, or otherwise treat them before use so that no sintering, or local fusion, of the surface, with consequent formation of irregular spaces, takes place in the. contact tube, or furnace. The pieces, or lumps, may preferably contain 30 per cent. or more of an oxid of a metal of the iron group or of a mixture of more than one of the said oxids and may be dense or porous, it being particularly advantageous in the former case to employ pieces, or lumps, produced by breaking up a mass obtained by allowing an oxidized melt to solidify. Or a suitable stable contact mass may be obtained by burning pure iron powder in a current of oxygen, so that a molten oxid is produced, and then breaking up the solidified mass into pieces, or lumps, of about the size of a pea, or millet or still larger. Use can, however, be made of other pieces, or lumps, such, for instance, as those obtained by breaking up sufiiciently pure Application filed February 25, 1915. Serial No. 10,627.

stance, a hydroxid of iron, of manganese, of

chromium, or of uranium, or a mixture of su-chhydroxids, may be precipitated by ammonia, or ammonium carbonate, or soda, from a solution of a suitable salt, or suitable salts, for instance, nitrates, or sulfates, and, after being well washed and sufliciently deprived of water, the precipitate can be pressed to form pieces, or lumps; or a part of the washed hydroxid ma be dried, at say about 250 centigrade, t en intimately mixed with the remaining damp portion and made into pieces, or lumps, of any desired shape such, for instance, as cubes, cylinders, spheres, or'the like. The pieces, or lumps, are preferably heated, to say from 500, to 700, centigrade before being used. We may also startfrom metallic pieces, or lumps, for instance, from a number of small spheres, or the like, of pure iron, which may be placed in the contact tube, or furnace, elther without treatment, or after being superficially oxidized.

The length of the layer of the contact mass, and the velocity of the gases, and the temperature employed, mayvary consider- 1 ably. Compounds which in uriously affect the catalytic action should not be present taining amolten and again solidified oxid of a metal of the iron group.

2. A process of producing oxide of nitrogen which comprises passing a, mixture of ammonia, and oxygen containing gas at an elevated-temperature over a catalyst containing a molten and again solidified oxid of a metal of the iron group. 1

In testimony whereof We have hereunrboset our hands in the presence of two sub- 10 scribing Witnesses.

CARL BCSCH. ALVJIN nHTTASC-H. CHRISTUPH BECK. iVitnesses:

ARTHUR DENONVILLE, JoHANNEs FEHMEL. 

